Polychlorinated biphenyls, or "PCB's" were long used as dielectric fluids in electrical equipment because these materials have excellent heat stability, are nonflammable in nature, have low volatility and a good viscosity characteristic at operation temperatures. Because of their environmental persistence, however, continued manufacture, import, or use in the United States was banned under the Toxic Substances control Act of 1976, and the U.S. Environmental Protection Agency was directed to promulgate rules and regulations for their removal from the economy.
As of July 1, 1979, EPA regulations defined as "PCB-contaminated" any material containing more than 50 ppm of a mono-, di-, or polychlorinated biphenyl. The regulations permit disposal of PCB-contaminated materials by either incineration in an approved manner or in an approved landfill, but such procedures have rarely proven acceptable to community neighbors. Since considerable fractions of the transformer oils, e.g., refined asphaltic-base mineral oil, or heat exchange oils, e.g., hydrogenated terphenyls, now in service are PCB-contaminated, the problem of disposing of PCB-contaminated hydrocarbon oils in an effective manner presents a serious challenge. As used hereinafter, the term "transformer oil" signifies a mineral insulating oil of petroleum origin for use as an insulating and cooling media in electrical apparatus, for example, transformers, capacitors, underground cables, etc.
Various techniques for meeting this challenge have been proposed. One method is shown by D. K. Parker et al, Plant engineering, Aug. 21, 1980, Pages 133-134. The method of Parker et al is based on the formation of a solution of an organo-sodium reagent, such as sodium naphthalenide, in a carrier solvent, for example, tetrahydrofuran, which is then added to the contaminated oil. The Parker et al process requires a multistep procedure involving first the formation of organo-sodium reagent, next the incorporation of such organo-sodium compound into the PCB-contaminated oil followed by at least 2 more hours for the reaction to be complete, followed by a water quench and distillation and purification steps to recycle the tetrahydrofuran. Another procedure, somewhat similar to the Parker et al process, is described by Smith et al, University of Waterloo, based on the graduate thesis of James G. Smith and G. L. Bubbar, "The Chemical Destruction of Polychlorinated Biphenyls by Sodium Naphthalenide". Again, a lengthy, multistep procedure is necessary before effective destruction of the PCB is achieved. A further procedure is shown by Hiraoka e al, Japan Kokai 74,822,570, Chem. Abstracts 8988831K, Vol. 82, 1975, which describes the destruction of polychlorinated biphenyls utilizing a sodium dispersion in Kerosene, but requires a 6 hour heating period at 120.degree. C.
Recently, Lewis L. Pytlewski et al, demonstrated that PCB's, as well as representative halogenated pesticides were found to be rapidly and completely decomposed by the use of molten sodium metal dispersed in polyethyleneglycol. The Pytlewski et al technique is shown in the reaction of PCB's with sodium, oxygen, and polyethyleneglycols, Chemistry and Biosciences Lab, Franklyn Research Center, Philadelphia, Pa. 19103. However, the use of metallic sodium metal requires the special handling and trace amounts of water must be eliminated to minimize dangerous side reactions.
In my copending application Ser. No. 269,121, filed June 1, 1981, I found that PCB's could be destroyed or effectively removed from transformer oil, or other inert organic solvents, by reaction of the PCB contaminated solvent with a polyoxyalkyleneglycol and alkali metal hydroxide at a temperature up to about 200.degree. C.
The present invention is based on my discovery that substantially improved results can be achieved with respect to rate of PCB removal from contaminated organic solvents by using mono-capped polyalkyleneglycol, C.sub.(1-4) alkyl ethers, for example, monocapped polyethyleneglycol methylethers (PEGM) with alkali metal hydroxides, for example, potassium hydroxide. I have found that a 3-5 fold increase in reaction rate results for either completely eliminating, or substantially reducing polyhalogenated aromatic hydrocarbon in substantially inert organic solvents by the practice of the present invention as compared to the method described in Ser. No. 269,121.